The value of urinalysis in presumptive diagnosis of urinary tract infection in children.

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Paediatrica Indonesiana

VOLUME 48 July NUMBER 4

Original Article

The value of urinalysis in presumptive diagnosis of

urinary tract infection in children

Dedi Rachmadi, Andaningrum Setyastuti

Abstract

BackgroundDefinite diagnosis of urinary tract infection (UTI) should only be established based on culture of urine specimen, otherwise it would be considered presumptive. Since urinalysis provides more rapid information than urine culture, clinicians should consider to utilize urinalysis as a decision-making tool for initiating treatment of UTI.

ObjectiveTo determine the sensitivity, specificity, predictive val-ues, and accuracy of several urinalysis parameters, namely the ni-trite, leukocyte esterase (LE), Gram staining, and methylene blue reductase (MBR) tests, in supporting the diagnosis of UTI.

Methods7KLVGLDJQRVWLFWHVWZDVGRQHRQVXEMHFWVZLWKS\XULD

GXULQJWKHSHULRGRI$SULOWR-XQH7KHVHQVLWLYLW\VSHFLILF -ity, positive predictive value (PPV), negative predicitve value (NPV) as well as the accuracy were calculated for each urinalysis parameter with urine culture as the gold standard. The relation-ship between categorical variables was analyzed by Fisher’s exact test or chi square test.

ResultsThe sensitivity, specificity, PPV, NPV and accuracy for nitrite test, leukocyte esterase (LE) test, Gram staining, and MBR

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ConclusionsThe MBR, among other urinalysis routine tests, has the highest specificity and accuracy as well as high sensitivity in establishing a presumptive diagnosis of UTI[Paediatr Indones 2008;48:199-203].

Keywords: presumptive diagnosis, urinalysis, UTI

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University, Dr. Hasan Sadikin Hospital, Bandung, Indonesia.

Request reprint to: Dedi Rachmadi, MD, Department of Child Health,

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he term urinary tract infection (UTI) denotes infection within the urinary tract and encompasses both renal parenchyma and urinary bladder infection. This infection is important in childhood because of its symptoms that may be either troublesome or overlooked and the potential risk of renal involvement. Early recognition and appropriate treatment of such patients are essential in order to preserve renal function and prevent permanent damage.3

The symptoms of children with UTI depend on the level of the infection as well as the age of the child. In classical acute pyelonephritis, patients have high fever and other systemic symptoms accompanied by back or flank pain and renal tenderness. However, symptoms of lower urinary tract such as dysuria, frequent voiding and incontinence are usually not detected in infants but it might be identified in pre-school and pre-school-age children.

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is relatively expensive and requires several days to find out the results. Urinalysis might be very helpful in providing immediate information to support the diagnosis of a UTI, hence prompt initiation of treat-ment is possible. Several urinalysis parameters for making a presumptive diagnosis of UTI are leukocyte esterase (LE), nitrite, Gram staining and methylene blue reductase (MBR) tests. To our knowledge no

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of the study was to obtain the sensitivity, specificity, positive predictive values, ,and accuracy of the nitrite, LE, Gram staining and MBR tests in the diagnosis of UTI in children.

Methods

A cross-sectional study on all children with pyuria who were admitted to Pediatric Outpatient Department and Pediatric Emergency Department of Hasan Sadikin Hospital was performed during the period April to

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and parents were interviewed regarding the history of illness and symptoms. Gender, age, physical findings, and laboratory results were recorded. The specimens for urinalysis were obtained by clean-catch mid stream

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age whose samples were taken by suprapubic aspiration. All urine specimens were collected in sterile containers without urine preservatives, transported immediately to the laboratory, and processed for urinalysis and culture.

Quantitative cultures were performed by the microbiology laboratory with pour plate method. A positive urine culture was defined as growth of

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nitrite and LE test (Ames Multistix reagent strip read

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Elkhart, Ind) on unspun urine. The results of LE and

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respectively, and reported as positive or negative. Smears were prepared using centrifuged urine that were air dried, and Gram stained. It was considered positive when bacteria were seen on any of the ten oil-immersed microscopic fields. MBRT test was done

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ml of urine and watching for the discoloration. This

test was considered positive if discoloration occurred within 6 hours.

Sensitivity, specificity, positive and negative predictive values, and the accuracy were calculated for each test with a positive urine culture as the gold standard. Relationship between categorical variables were analyzed by Fisher’s exact test or the chi square test.

Results

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months old. Age and sex distribution of the subjects is shown in Table 1.

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days). Local symptoms of UTI, i.e., dysuria, frequency,

XUJHQF\RUHQXUHVLVZHUHIRXQGLQVXEMHFWVZLWK WKHPHDQGXUDWLRQRIGD\V6'GD\VUDQJH GD\V Table 2 shows that neither fever nor local symptoms of UTI had statistically significant

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urine culture showed that Escherichia coli was the

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Thirty urine specimens were tested for nitrite and LE dipsticks t, Gram staining, and MBR. The

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association of of each test and urine culture is shown in Table 3. Sensitivity, specificity, predictive values and accuracy of each test were calculated using urine culture as the gold standard as shown in Table 4.

Discussion

Our study showed that boys were more affected by UTI than girls in infancy, whereas girls were the predominant proportion in older children. This result was similar with the study of Winberg et al5_which

stated that with increasing age, there was a progressive increase in the incidence among females compare to males.5,6_{The reasons were that male infants are}

more sensitive to infection due to immaturity of the immunologic defense mechanisms7_{and higher ratio}

of urinary tract obstructive malformations.8_The

increasing incidence of UTI in girls compared to boys has been attributed to the shorter length of the female urethra providing easy access to the bladder. Aside from that, older girls have high susceptibility for periurethral colonization with Gram negative bacteria.9

Table 2 shows that neither fever nor local symp-toms of UTI had statistically significant association with positive urine culture. Positive urine culture

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-ent results were caused by the differ-ent designs of the studies. In our study, urine samples were taken from subjects with pyuria, whereas those studies involved subjects with symptoms suggestive for UTI. Specimens for urinalysis in our study were obtained by midstream urine method and suprapubic aspiration for children

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studies used various collection methods except with urine bag.

In this study, we found no statistically significant associations between either nitrite, LE, Gram staining, or MBR tests and the results of urine culture. The calculated sensitivity, specificity, and PPV of fever in

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better diagnostic value than fever in diagnosing UTI. All of those values were lower than those reported by

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urine culture is the gold standard of UTI diagnosis, both fever and local symptoms should not be used as a diagnostic tool, but only as supporting tools in making presumptive diagnosis of UTI.

Escherichia coli were the most common organ-isms growing in urine culture. This finding was similar to that of previous studies. Predominance of E. coli was mainly attributed to some characteristics that was not found in other organisms, such as p-fimbriae, adherence to uroepithelium in O and K serotype, hemolysin production, and the resistance to the bac-tericidal action or normal human serum.

For many years clinicians have used Gram– staining urine for screening test of UTI in symptom-atic outpatients. In an extensive review, Jenkins et al concluded that examination of a Gram-staining smear of uncentrifuged specimen provided the best microscopic method for detecting bacteriuria. Several previous studies in adults howed that LE and nitrite tests could be used for screening test of UTI, but only the study by Goldsmith and Campos had addressed this issue in pediatric patients.

Table 4 shows that the test with highest sensitiv-ity was Gram staining of urinary smear. This result was similar with that of Olsonet al The test with lowest sensitivity was MBR. The sensitivity of nitrite test in this study was higher than that reported by Goldsmith and Campos, Weinberg and Gan, and Hoberman and Wald. The sensitivity of LE test was also higher than that of previous studies.

The test with highest specificity was MBR,

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specificities of nitrite, LE test, and Gram staining were lower than those reported by others.

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tests were lower than those reported by Hoberman and Wald. The PPV of Gram staining was higher than that reported by Weinberg and Gan.

The highest NPV was obtained from Gram

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tests. The NPV of Gram staining was similar to that of Weinberg and Gan study,while the NPV of dipstick tests was lower than that of another study.

The MBR test in this study has sensitivity of

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theother tests. The accuracy of nitrite test, LE test and

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-tively. Hence, the MBR test was the best for detecting significant bacteriuria. This result was similar as that reported by Supardi. It was concluded that among other urinalysis routine tests, MBR has the highest specificity and accuracy, as well as high sensitivity in establishing a presumptive diagnosis of UTI.

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microscopy, and culture for the detection of bacteriuria in

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slide centrifuge gram stain as an urine screening method. Am

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kimiawi dan biakan air kemih untuk diagnostik